Bags made of thin polyethylene material have been used in various sizes. Small bags are used in packaging of sandwiches and the like, medium size bags are used for garbage and kitchen trash and larger bags are used for other types of trash such as lawn clippings and leaves. Bags of this type generally include a front wall and back wall and are seamed up the sides with an open top. The top is adapted to be closed by twisting and maintained closed by a suitable tie strip or string. The present invention is particularly concerned with a novel bag tie closure for thermoplastic bags. In the past, thermoplastic bags have been provided with various types of tie strips. In some instances the tie strips have been separate strips adapted to be wrapped around the neck of the bag, such strips having openings and notches thereon to effect a closure of the strip around the neck of the bag. In other instances a flat tie strip has been secured to the top of the bag by an adhesive patch so that the tie strip can be removed from the bag and wrapped around the neck of the bag after it has been filled to effect closure of the bag. In other instances, the neck of the bag has been closed by sticky tape and in other instances the bags have been closed by banding the neck of the bag with adhesive. While these various techniques of closing the neck of the bag have been used successfully, they have left something to be desired.